1994 Kia Sephia LS, AutomaticFACTORY OEM SERVICE PROCEDURE

Code 15: Oxygen Sensor (O2S)

  1. Check O2S connector for poor connection. Clean or repair connector as necessary. If connector is okay, go to next step.
  2. Ensure engine is at normal operating temperature. Disconnect O2S connector. Connect voltmeter between O2S and ground. Start engine and raise engine speed to 3000 RPM until voltmeter indicates .55 volt. Increase and decrease engine speed rapidly several times. When engine speed is increased, voltage should be .5-1.0 volt. When engine speed decreases, voltage should be 0-.4 volt. If voltage is as specified, go to next step. If voltage is not as specified, replace O2S.
  3. Disconnect O2S. Using an ohmmeter, check continuity of Blue/Red wire between O2S connector and terminal No. 20 of ECM C249 (26-pin) connector. If continuity exists, go to next step. If continuity does not exist, repair open Blue/Red wire between O2S connector and ECM connector.
  4. Reconnect O2S connector. Check voltage at terminal No. 20 (Blue/Red wire) of ECM C249 (26-pin) connector while performing the following. Start engine and raise engine speed to 3000 RPM until voltmeter indicates .55 volt. Increase and decrease engine speed rapidly several times. When engine speed is increased, voltage should be .5-1.0 volt. When engine speed decreases, voltage should be 0-.4 volt. If voltage is as specified, replace ECM. If voltage is not as specified, located and repair short in wiring between O2S and ECM connector.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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